FLRT proteins are endogenous latrophilin ligands and regulate excitatory synapse development

Latrophilins (LPHNs) are a small family of G protein-coupled receptors known to mediate the massive synaptic exocytosis caused by the black widow spider venom α-latrotoxin, but their endogenous ligands and function remain unclear. Mutations in LPHN3 are strongly associated with attention deficit hyperactivity disorder, suggesting a role for latrophilins in human cognitive function. Using affinity chromatography and mass spectrometry, we identify the FLRT family of leucine-rich repeat transmembrane proteins as endogenous postsynaptic ligands for latrophilins. We demonstrate that the FLRT3 and LPHN3 ectodomains interact with high affinity in trans and that interference with this interaction using soluble recombinant LPHN3, LPHN3 shRNA, or FLRT3 shRNA reduces excitatory synapse density in cultured neurons. In addition, reducing FLRT3 levels with shRNA in vivo decreases afferent input strength and dendritic spine number in dentate granule cells. These observations indicate that LPHN3 and its ligand FLRT3 play an important role in glutamatergic synapse development.     

Role of Synthesized Organoselenium Compounds on Protection of Rat Erythrocytes from DMBA-Induced Oxidative Stress

Formation of free radicals is not limited to normal cellular process but also occur upon exposure to certain chemicals (polycyclic aromatic hydrocarbon, cadmium, lead, etc.), cigarette smoke, radiation, and high-fat diet. Free-radical damage is an important factor in many pathological and toxicological processes. Selenium, an essential micronutrient, is a associated with antioxidant functions, physiological defense mechanisms against different diseases including several types of cancers. Search for new selenium compounds with more chemopreventive activities and less toxicities are in progress. In addition, there has been a growing interest in the synthesis of organoselenium compounds with respect to their use in enzymology and bioorganic chemistry. In the present study, adult female Wistar rats were treated with 7,12-dimethylbenz[a]anthracene (DMBA) and the organoselenium compounds [1-isopropyl-3-methylbenzimidazole-2-selenone (Se I) and 1, 3-di-p-methoxybenzylpyrimidine-2-selenone (Se II)] in determined doses. The protective effects of synthetic organoselenium compounds (Se I and Se II) against DMBA-induced changes in antioxidant enzyme (superoxide dismutase, glutathione peroxidase (GSH-Px), catalase (CAT), glutathione reductase (GR)) activities, total GSH, and malondialdehyde (MDA) levels of rat erythrocyte were investigated. The DMBA-treated group exhibited significant decreases in the levels of erythrocyte GSH-Px, CAT, and GR activities, an increase in MDA levels, and a decrease in total GSH level compared to the control. Se I and Se II fully or partially restored enzyme activity. Lipid peroxidation was also decreased in Se-I- and Se-II-treated groups.     

Role of selenium compounds on tyrosine hydroxylase activity,adrenomedullin and total RNA levels in hearts of rats

Synthetic organoselenium compounds can be tailored to achieve greater chemopreventive efficacy with minimal toxic side effects by structural modifications. Two organoselenium compounds (Se I and Se II) were synthesized and evaluated for their antihypertensive and therapeutic properties by adrenomedullin (ADM) levels and tyrosine hydroxylase (TH) activity assays in rat heart tissue. 7,12-Dimethylbenz[a]anthracene (DMBA) is known to generate DNA-reactive species during their metabolism, which may enhance oxidative stress in cells. TH is thought to be a rate-limiting enzyme in the biosynthesis of catecholamines. ADM, a potent endogenous vasodilating and natriuretic peptide, may play an important role in the pathophysiology of chronic heart failure. The effects of Se I and Se II were investigated on TH activity, ADM and total RNA levels in the hearts of albino Wistar rats. TH activity was found to be increased significantly by the effect of DMBA (P < 0.05). This increase was restricted in the Se I and Se II treated groups. ADM level was found to be decreased insignificantly by the effect of DMBA (P > 0.05). Total RNA level was found to be decreased significantly by the effect of DMBA (P < 0.05). This study demonstrates that synthetic organoselenium compounds can regulate DMBA-induced stress related changes in rat heart.     

Zoledronic acid is synergic with vinblastine to induce apoptosis in a multidrug resistance protein-1 dependent way: an in vitro study

We have explored the action of zoledronic acid, which has an apoptotic effect and is used as an agent for treating skeletal metastases and osteoporosis, in the presence of vinblastine, and whether this effect is associated with MRP-1 (multidrug resistance protein-1) expression. HEK (human embryonic kidney) 293 cells were transfected to form the multidrug resistant cell line designated 293MRP (MRP-1 expressing HEK293 cells). Both lines were treated with varying concentrations of vinblastine and zoledronic acid. Apoptosis was determined by the TUNEL (deoxyuridine triphosphate nick end-labeling) method. The type of treatment, MRP-1 expression status, and the type of treatment with respect to MRP-1 expression status significantly affected (P < 0.001) the degree of apoptosis. The largest increase in cytotoxicity was noted in HEK293 cells, when 100 micromol zoledronic acid was added to 4 microg/ml vinblastine (an increment of 80.3%, P < 0.001). This preliminary work shows that zoledronic acid acts synergistically with vinblastine to induce apoptosis in an MRP-1 dependent way.     

Effects of erythropoietin and pentoxifylline on the oxidant and antioxidant systems in the experimental short bowel syndrome

In this study, we investigated the effects of erythropoietin (Epo), and pentoxifylline (Ptx) on the oxidant and antioxidant systems in the experimental short bowel syndrome. Spraque-Dawley rats were divided into four groups and all animals underwent 75% small bowel resection. Group E was treated with 500 IU kg(- 1) Epo subcutaneously (s.c.), group P with 50 mg kg(- 1) day(- 1) s.c. Ptx and group E+P with 500 IU kg(- 1) s.c. Epo plus 50 mg kg(- 1) day(- 1) s.c. Ptx for a period of 28 days. In group C, which is the control group, no drug treatment was given. At the end of 28 days the experimented rats were killed and ileum samples excised for biochemical and histopathological testing. Malondialdehyde (MDA), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) levels were determined in ileum homogenates. When compared to group C, the MDA and GSH-Px levels were significantly decreased (p < 0.05), but SOD activity was not changed (p > 0.05) in groups P and E+P, whereas both MDA and SOD and also GSH-Px activities were not changed significantly in group E (p > 0.05). The average villous length, crypt depth, muscular thickness and mucosal length were measured in all groups. The average crypt depth and mucosal length were statistically higher in the group P than group C (p < 0.001, p < 0.01, respectively). In addition, the crypt depth was statistically higher in both E and E+P groups as compared to group C (p < 0.001, p < 0.01, respectively). Therefore, our study indicates that Ptx may be more effective than Epo in reducing lipid peroxidation. Moreover, we considered that Ptx may give this protective effect by inhibiting the free oxygen radicals to a greater extent than developing the antioxidant capacity.     

Inhibition of DMBA Induced Rat Mammary Duct Damage by Novel Synthetic Organoselenium Compounds.

The balance between prooxidants and antioxidants is crucial to the survival and functioning of aerobic organisms. Partially reduced derivatives of oxygen, which are produced in aerobic organisms as part of normal physiological and metabolic processes, are toxic species, oxidizing numerous biomolecules, which initiate tissue injury and cell death. DMBA (7,12-dimethylbenz[a]anthracene) is a polycyclic aromatic hydrocarbon (PAH) known to cause tumors in rats. DMBA is known to generate DNA-reactive species, which may enhance oxidative stress in cells, during its metabolism. Besides the formation of DNA adducts, oxidative products derived from mutagen metabolism, such as DMBA, might impair vital cellular functions by damaging proteins and lipid membranes. Synthetic organoselenium compounds inhibit the initiation phase of carcinogenesis by inhibiting DMBA-DNA adduct formation in the target organ in vivo. Because of the health problems induced by many environmental pollutants, many efforts have been undertaken to evaluate the relative antioxidant potential of selenium and synthetic organoselenium compounds. We undertook the present study to evaluate the chemopreventive potential of the novel synthetic organoselenium compounds (1-isopropyl-3-methylbenzimidazole-2-selenone (SeI) and 1,3-di-p-methoxybenzylpyrimidine-2-selenone (SeII)) in the well-established DMBA-treated rat model by monitoring the extent of lipid peroxidation and mammary duct damage. In this study, adult female Wistar rats were treated with DMBA and the novel organoselenium compounds (SeI and SeII) in determined doses. In DMBA-treated rats, the effects of the organoselenium compounds on malondialdehyde (MDA) levels and histological changes in the rat mammary lactiferous duct were studied. The ability of the organoselenium compounds to prevent oxidative damage induced by DMBA in rat mammary ducts was demonstrated. Protection against lipid peroxidation measured as MDA in the SeI and SeII treated groups was provided by the novel synthesized organoselenium compounds. SeI and SeII both provided chemoprevention against DMBA-induced oxidative stress in the rat mammary duct.     

Multidrug Resistance-Associated Protein 1 (MRP1) mediated vincristine resistance: effects of N-acetylcysteine and Buthionine Sulfoximine

Background  

Multidrug resistance mediated by the multidrug resistance-associated protein 1 (MRP1) decreases cellular drug accumulation. The exact mechanism of MRP1 involved multidrug resistance has not been clarified yet, though glutathione (GSH) is likely to have a role for the resistance to occur. N-acetylcysteine (NAC) is a pro-glutathione drug. DL-Buthionine (S,R)-sulfoximine (BSO) is an inhibitor of GSH synthesis. The aim of our study was to investigate the effect of NAC and BSO on MRP1-mediated vincristine resistance in Human Embryonic Kidney (HEK293) and its MRP1 transfected 293MRP cells. Human Embryonic Kidney (HEK293) cells were transfected with a plasmid encoding whole MRP1 gene. Both cells were incubated with vincristine in the presence or absence of NAC and/or BSO. The viability of both cells was determined under different incubation conditions. GSH, Glutathione S-Transferase (GST) and glutathione peroxidase (GPx) levels were measured in the cell extracts obtained from both cells incubated with different drugs.     

Identification of peroxisome proliferator-responsive human genes by elevated expression of the peroxisome proliferator-activated receptor alpha in HepG2 cells

In mice and other sensitive species, PPARalpha mediates the induction of mitochondrial, microsomal, and peroxisomal fatty acid oxidation, peroxisome proliferation, liver enlargement, and tumors by peroxisome proliferators. In order to identify PPARalpha-responsive human genes, HepG2 cells were engineered to express PPARalpha at concentrations similar to mouse liver. This resulted in the dramatic induction of mRNAs encoding the mitochondrial HMG-CoA synthase and increases in fatty acyl-CoA synthetase (3-8-fold) and carnitine palmitoyl-CoA transferase IA (2-4-fold) mRNAs that were dependent on PPARalpha expression and enhanced by exposure to the PPARalpha agonist Wy14643. A PPAR response element was identified in the proximal promoter of the human HMG-CoA synthase gene that is functional in its native context. These data suggest that humans retain a capacity for PPARalpha regulation of mitochondrial fatty acid oxidation and ketogenesis. Human liver is refractory to peroxisome proliferation, and increased expression of mRNAs for the peroxisomal fatty acyl-CoA oxidase, bifunctional enzyme, or thiolase, which accompanies peroxisome proliferation in responsive species, was not evident following Wy14643 treatment of cells expressing elevated levels of PPARalpha. Additionally, no significant differences were seen for the expression of apolipoprotein AI, AII, or CIII; medium chain acyl-CoA dehydrogenase; or stearoyl-CoA desaturase mRNAs.